Theoretical and experimental elucidation of synergistic enhanced piezo-photocatalysis and mechanism of BiVO4 for organic pollutant degradation

Herein, we have synthesized BiVO4 (BVO) square bricks and spherical particles to elucidate the piezo-photocatalytic performance and involved synergistic mechanism. The photocatalytic, piezocatalytic and piezo-photocatalytic experiments were carried out under irradiation of simulated sunlight, ultrasonic wave and both of them, respectively. The degradation of methylene blue (MB) reveals that, for both BVO bricks and particles, the piezo-photocatalysis is greater than single photocatalysis and piezocatalysis, obviously manifesting a synergistic piezo-photocatalytic behavior according to the "1 + 1 > 2″ principle. The BVO bricks exhibit a higher synergistic effect than spherical particles, which is mainly due to the fact that photoexcited carriers in the square bricks can be directionally forced, by ultrasonic-induced polarization field, to specific surfaces. Density functional theory (DFT) calculation combined with finite-element method (FEM) simulation was performed to elucidate the piezo-photocatalytic mechanism of BVO. Moreover, the degradation pathways of MB and toxicities of degradation intermediates were analyzed.